what to cover

Hi class.
Can you do a niche site? Can you do a blogger? The answer is yes. The thing to look for is whether the site is interesting. Are they doing something new or different? If they are just linking for example, you may not have much to write about. If they are linking and commenting and producing stories or analysis, then you have more to report on. If they are producing conent, terrific.
A niche site, a site or blog on a certain topic , is fair game for sure. Many political sites are exactly that - and some have become quite famous.
One caveat - a purely personal site can be tricky unless it is very good, very well done and has received some attention. A personal blog detailing someone's daily life may not yield much in the way of a good story.
Hope that helps.
Paul